Examples of an apparatus are disclosed. In some example, an apparatus may include a photodiode, a first charge storage unit configured to store charges generated by the photodiode, the first charge storage unit having a first capacity; and a second charge storage unit configured to store charges generated by the photodiode, the second charge storage unit having a second capacity greater than the first capacity. The apparatus may further include an analog-to-digital converter (ADC) circuit configured to measure a first quantity of charges stored in the first charge storage unit and a second quantity of charges stored in the second charge storage unit, and to generate a digital output representing an intensity of light incident on the photodiode based on a first count representing the first quantity of charges or a second count representing the second quantity of charges.